This invention relates to a switch assembly and more particularly to a linear motion switch assembly adapted to selectively energize and properly position any one of two lamps from a single power source and to assure that the lamp selected is properly aligned with respect to an optical system.
The prior art is well aware of the problem of employing a plurality of back-up bulbs or lamps to provide quick replacement of the one being utilized if a failure occurs. Such techniques provide a minimum down-time for the optical system to enable one to rapidly replace a failed lamp by a switching action instead of actually removing the lamp from the socket and replacing the same.
It is also apparent that when one employs such a back-up lamp source in a relatively accurate optical system, one must be assured that a selected lamp or bulb will move into proper registration with either a lens system or an outlet aperture to assure and maintain optical system performance.
The prior art is replete with a number of patents and techniques which allow one to switch lamps without removing a failed unit from its socket or holder. A particularly useful approach is depicted in U.S. Pat. No. 3,959,612 issued on May 25, 1976 entitled ROTARY SWITCH ASSEMBLY PARTICULARLY ADAPTED FOR USE WITH FIBER OPTIC LIGHT SOURCES by Richard E. Feinbloom and assigned to the assignee herein. This patent gives examples of various other patents as prior art which are pertinent to the general problem of switching a defective bulb.
As indicated in that patent, a particular important reason for providing such structure is necessitated by the constraints imposed in a medical or dental procedure. In regard to such procedures a "cold light" source is employed during a surgical or operating room procedure. Essentially, the cold light source comprises a fiber optic cable which is illuminated by a high intensity, high wattage lamp. The filament of the light source or lamp is positioned to illuminate an inlet port of the fiber optic cable, which cable may be a few feet or more in length. The lamp or light source is housed in a suitable enclosure, where, because of its high power dissipation, it produces substantial amounts of heat. As such the lamp and housing have to be cooled by means of a fan or other suitable arrangement.
The surgeon or dentist uses the fiber optic cable as a light source and he can therefore direct the light emanating from the outlet end of the fiber cable to any desired position. Since the fiber optic cable is a good conductor of light and because of the optical properties it does not conduct the heat generated by the lamp in the enclosure. Hence the term "cold-light" source has been used to describe such a device.
The amount of light needed for surgical procedures as well as dental procedures is substantial. Due to this fact lamp sources such as halogen, xenon or other high intensity lamps are employed. These lamps operate at high wattage and have a relatively small average life which may be between 10 to 30 hours.
Based on these considerations the lamp or bulb can be expected to fail during use, which in the case of a surgical or dental procedure may endanger the patient as unduly delaying the operation.
Thus the failure of a light source during such a procedure can seriously endanger the operating technique and place the patient in a hazardous position. Moreover, due to the extreme heat generated by the assembly, it becomes difficult to physically replace the unit until it cools. Furthermore, there is always the possibility that another lamp or bulb is not available hence creating further difficulty.
Apart from such considerations is the fact that the bulb cannot be merely replaced as one would do in a typical fixture.
As indicated, the alignment of the optical axis of the bulb with the inlet of the fiber cable is important, so that the light is properly directed to provide a desired output pattern. Therefore, the switching assembly is accurately fabricated to assure that each bulb is properly aligned to enable selection of either bulb within the housing.
The above noted problems are described in U.S. Pat. No. 3,959,612 which shows apparatus solving the problems. In the apparatus according to that patent a rotary switch is employed which switch allows one to select any one of four bulbs.
While the apparatus is reliable it is relatively expensive and complicated and offers a great deal of back-up which is not necessary in many typical procedures, as for example, in the field of dentistry.
It is therefore an object of the present invention to provide an improved switching assembly for selecting one of two lamp assemblies in a simple and rapid manner while assuring that the selected unit is in proper alignment when selected as being optimumly positioned with respect to the fiber optic cable and the light source housing.